Jeff Jorgensen <[EMAIL PROTECTED]> writes: > Hello, > > I have set up a data.frame and one of the columns contains a date of > the form (with slashes as separators): > > mm/dd/yyyy > > I would like to use formulas on other columns in the data.frame > organized by date, for example: > > tapply(var1, sort(date), mean)
I don't think that does what I think you think it does! > However, when I try sort(date) it sorts based on the first two entries > in the date field: > > 9/1/2001 9/1/2002 9/1/2003 9/2/2001 ... > 5.6 7.5 6.4 7.0 ... > > Instead of: > > 9/1/2001 9/2/2001 9/3/2001 9/4/2001 ... > 5.6 6.1 7.2 6.8 ... > > I would greatly appreciate any help in sorting chronologically. Do I > need to create separate columns for month, day, and year, and then use > order() and then stipulate the hierarchy for which to sort the output? > Or, is there some other more efficient way? You now know why the ISO standard has yyyy-mm-dd ... It's a bit awkward, but I think you need something like pdate <- as.POSIXct(strptime(date,"%m/%d/%Y")) tapply(var1, pdate, mean) -- O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
